Stöcker Tony, Shah N Jon
Institut für Medizin, Forschungszentrum Jülich GmbH, Jülich, Germany.
Magn Reson Med. 2006 Oct;56(4):824-34. doi: 10.1002/mrm.21011.
The magnetization-prepared rapid gradient-echo (MP-RAGE) sequence is well known and widely used for high-resolution, structural brain MRI. Here we present a new version, termed magnetization-prepared spiral acquisition gradient-echo (MP-SAGE), that employs interleaved square-spiral phase-encoding (PE) to take advantage of the 3D nature of the sequence. Resolution loss caused by point-spread function (PSF) blurring is circumvented by the use of variable flip angle (VFA) radiofrequency (RF) pulses. The pulse train is calculated by means of an accurate new signal evolution theory that is derived from the extended phase graph (EPG) description. Phantom results show excellent agreement between theory and experiment for substances with relaxation times similar to those of human brain tissue. Both phantom and in vivo results show a strong enhancement of SNR and CNR compared to the standard MP-RAGE in high-resolution MRI. The benefits for brain tissue segmentation using images obtained with MP-SAGE are shown.
磁化准备快速梯度回波（MP-RAGE）序列广为人知，并且被广泛用于高分辨率的脑部结构磁共振成像（MRI）。在此，我们展示了一个新版本，称为磁化准备螺旋采集梯度回波（MP-SAGE），它采用交错方形螺旋相位编码（PE）来利用该序列的三维特性。通过使用可变翻转角（VFA）射频（RF）脉冲，避免了由点扩散函数（PSF）模糊引起的分辨率损失。脉冲序列是通过一种基于扩展相位图（EPG）描述推导出来的精确新信号演化理论计算得出的。模体结果表明，对于具有与人类脑组织相似弛豫时间的物质，理论与实验结果高度吻合。模体和体内实验结果均表明，与标准MP-RAGE相比，在高分辨率MRI中，MP-SAGE的信噪比（SNR）和对比噪声比（CNR）有显著提高。文中展示了使用MP-SAGE获得的图像进行脑组织分割的优势。
